Temporary way for map renderers to register.

src/ol/renderer/MapRenderer.js

@@ -22,3 +22,48 @@ ol.renderer.MapRenderer = function(container) {
  */
 ol.renderer.MapRenderer.prototype.draw = function(layers, center, resolution, animate) {
 };
+
+/**
+ * TODO: determine a closure friendly way to register map renderers.
+ * @type {Array}
+ * @private
+ */
+ol.renderer.MapRenderer.registry_ = [];
+
+/**
+ * @param {Function} Renderer
+ */
+ol.renderer.MapRenderer.register = function(Renderer) {
+    ol.renderer.MapRenderer.registry_.push(Renderer);
+};
+
+/**
+ * @param {Array.<string>} preferences List of preferred renderer types.
+ * @returns {Function} A renderer constructor.
+ */
+ol.renderer.MapRenderer.pickRendererType = function(preferences) {
+    // map of candidate renderer types to candidate renderers
+    var types = {};
+
+    function picker(Candidate) {
+        var supports = Candidate.isSupported();
+        if (supports) {
+            types[Candidate.getType()] = Candidate;
+        }
+        return supports;
+    }
+    var Candidates = goog.array.filter(ol.renderer.MapRenderer.registry_, picker);
+    
+    // check to see if any preferred renderers are available
+    var Renderer;
+    for (var i=0, ii=preferences.length; i<ii; ++i) {
+        Renderer = types[preferences[i]];
+        if (Renderer) {
+            break;
+        }
+    }
+    
+    // if we didn't find any of the preferred renderers, use the first
+    return Renderer || Candidates[0] || null;
+};
+